The accidental exposure of a scientist to the Ebola virus last week[2] has triggered a series of teleconferences by Ebola scientists on two sides of the Atlantic united around a single goal: to help save the life of their colleague, an unnamed virologist at the Bernard Nocht Institute for Tropical Medicine in Hamburg, Germany, who pricked herself in the finger during an experiment. No approved treatments exist for Ebola, but at the sessions, researchers and physicians discussed the results from a raft of recent studies, some not yet published, into treatments that could prevent or slow the disease, which has a mortality rate of up to 90%.

In the end, the patient and her doctor opted not for an experimental drug but for a new type of living vaccine that has never been tested in humans but has been shown in monkeys to help fight the virus even when given after exposure. An injury from a virus-laden syringe often doesn't lead to infection and disease, because the amount of virus entering the body is small. But the researcher's doctors want to reduce the risk as much as they can.

Today was the 6th day after the needle accident, and the small community of Ebola researchers has been anxiously following news about the researcher's fate.

She is currently doing well, says Stephan Günther, the head of virology at the Bernard Nocht Institute. But Ebola can have an incubation period anywhere between 4 and 21 days, which means she could still fall ill. In monkeys, the virus is usually detectable in the blood starting on day 3, 4, or 5, says Boston University virologist Thomas Geisbert, who has more experience than any other researcher with the virus in animals. That may be different in humans, Geisbert stresses, but still, "the chances that she'll be okay are getting better every day."

Immediately after the researcher pricked herself last Thursday, Günther says he tried to assemble the best minds in the field. During a series of teleconferences--which included researchers from the Canadian Science Centre for Human and Animal Health in Winnipeg, the U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID) in Fort Detrick, Maryland, and the U.S. Centers for Disease Control and Prevention in Atlanta, Georgia--researchers discussed a long list of possible treatment options.

The vaccine that eventually was picked was developed by Heinz Feldmann and his colleagues at the Winnipeg lab along with Geisbert, who tested it in macaque monkeys at USAMRIID. The vaccine is based on the vesicular stomatitis virus (VSV), a pathogen of cattle, horses, and pigs, whose glycoprotein has been replaced with that of Ebola. In 2003, the researchers showed that a single shot of the virus offers protection in monkeys (Science, 14 November 2003, p. 1141[3]).

A lot of time was spent last week debating the safety aspects of the vaccine; because it is a living virus that replicates inside its hosts, some worry that it could prove risky. And in contrast to another Ebola vaccine based on DNA[4], it has never been tested in humans. But its key advantage is that, at least in monkeys, it has been shown to offer protection even after exposure, says Günther. In a 2008 study, Feldmann and Geisbert showed that when given 20 minutes after a lethal shot of Ebola-Sudan, one of the five subtypes of the virus, half of the monkeys got sick, but all survived. With Ebola-Zaïre, the subtype to which the researcher in Hamburg was exposed, five out of eight monkeys survived the virus. In as-yet-unpublished work, the researchers also gave a vaccine against Marburg, a close cousin of Ebola, 1 or even 2 days after exposure, says Geisbert, and they found that it still offered partial protection. He expects the same will be true for the Ebola vaccine.

Feldmann arranged shipment of the vaccine against Ebola-Zaire from Winnipeg the day the accident happened, and it reached the lab in Hamburg less than 48 hours after the accident, says Günther. (The researcher herself made the decision to have the vaccine, he says.) Meanwhile, a company called ARCA Biopharma, headquartered in Colorado, rushed to Hamburg a supply of an experimental anticoagulant drug called rNAPc2, which studies by Geisbert and colleagues have also shown to have promise against Ebola. But that has not been used so far, says Günther.

After she received the vaccine, the researcher began running a fever. Because it was unclear whether this was due to the onset of Ebola or a reaction to the vaccine, she was placed in an isolation unit, shielded from the world by plastic, says Günther. The fever is gone now, and doctors would like to take her out of the unit and back into a normal hospital ward, says Günther. "Psychologically, the isolation is very difficult," he says, and she could always be put back in should Ebola symptoms emerge. But the institute is "struggling a little" with Hamburg public health authorities reluctant to let the patient out, he says. Because so few Ebola cases occur in developed countries, there's no consensus on the right precautions.

The researcher was working on a study that involved mice, says Günther, who says he does not know the exact nature of the experiment. The last known lab exposure to Ebola, at USAMRIID in 2004, also involved mice. While a scientist tried to inject one of the animals using a hypodermic needle that had previously been used on other mice, researchers wrote in a 2008 paper[5] about the case, "the animal kicked the syringe, causing the needle to pierce the person's left-hand gloves, resulting in a small laceration." That researcher did not become infected, however.